Hydrocatalytic process for normal paraffin wax and sulfur removal

ABSTRACT

Hydrocarbon fractions, particularly petroleum fractions of 30650* C boiling range and containing 0.1 - 3.0 percent wt. sulphur 5-50 percent wt. n-paraffin wax, are reduced in sulphur and nparaffin wax content by hydrocatalytic treatment at 260*-482* C and 50-3,000 psig, first over a catalyst of a Group VI or VIII hydrogenating component on a mordenite of reduced alkali metal content to remove n-paraffin wax and then over a catalyst of a Group VI or VIII hydrogenating component and a refractary inorganic oxide to remove sulphur. Diesel fuels or fuel oils are separated from the desulfurized product. Preferred catalysts are Pt on decationized mordenite and CoMo on alumina used respectively in amounts of 10-90 and 90-10 percent vol., preferably 20-60 and 80-40 percent vol. The feedstock must contact the mordenite catalyst first since this is sensitive to H2S and if gas is recycled from the sulphur removal to the nparaffin wax removal stage this should be treated to remove H2S.

United States Patent Burbidge et al.

[ June 6, 1972 [54] HYDROCATALYTIC PROCESS FOR NORMAL PARAFFIN WAX ANDSULFUR REMOVAL The British Petroleum Company Limited, London, England 22Filed: Sept. 22, 1969 21 Appl.No.: 860,082

[73] Assignee:

[30] Foreign Application Priority Data Nov. 7, 1968 Great Britain..52,8l3/68 [52] U.S. Cl ..208/97, 208/11 1 [51] Int. Cl ..C10g 37/06[58] Field of Search ..208/58, 97, 211

[56] References Cited UNlTED STATES PATENTS 3,183,! 79 /1965 Schuman..208/97 3,338,819 8/1967 Wood ..208/97 3,438,887 4/l 969 Morris et al...208/87 3,472,759 /1969 Masologites et al. ..208/59 3,493,493 2/1970Henke et al ..208/264 3,5! 1,772 5/1970 Thompson ..208/1 12 PrimaryExaminerDelbert E. Gantz Assistant Examiner-G. J. CrasanakisAttorney-Morgan, Finnegan, Durham & Pine [57] ABSTRACT Hydrocarbonfractions, particularly petroleum fractions of -650 C boiling range andcontaining 0.1 3.0 percent wt. sulphur 5-50 percent wt. n-paraffin wax,are reduced in sulphur and n-paraffin wax content by hydrocatalytictreat- 7 ment at 260-482 C and -3,000 psig, first over a catalyst of aGroup V] or Vlll hydrogenating component on a mordenite of reducedalkali metal content to remove n-paraffin wax and then over a catalystof a Group V] or Vlll hydrogenating component and a refractary inorganicoxide to remove sulphur. Diesel fuels or fuel oils are separated fromthe desulfurized product.

Preferred catalysts are Pt on decationized mordenite and CoMo on aluminaused respectively in amounts of 10-90 and 90-10 percent vol., preferably20-60 and -40 percent vol. The feedstock must contact the mordenitecatalyst first since this is sensitive to H 5 and if gas is recycledfrom the sulphur removal to the n-paraffin wax removal stage this shouldbe treated to remove H S.

5 Claims, No Drawings HYDROCATALYTIC PROCESS FOR NORMAL PARAFFIN WAX ANDSULFUR REMOVAL This invention relates to the hydrocatalytic treatment ofhydrocarbon fractions and particularly to the removal of sulphur andn-paraffin wax from such fractions.

Hydrocarbon fractions particularly petroleum fractions are required tohave both a low sulphur content and a low pour point for many uses.Processes are known both for sulphur removal and for the removal ofn-parafiin wax, which are the main cause of high pour points inpetroleum fractions, but carrying out the processes separately isrelatively expensive. It has now been found that both steps can becarried out in the same reaction system provided certain precautions areobserved.

According to the present invention a hydrocatalytic process for theremoval of sulphur and n-paraffin wax from hydrocarbon fractionscomprises passing a hydrocarbon fraction containing sulphur compoundsand n-paraffin wax together with substantially sulphur-free hydrogen at260482 C and 50 3,000 psig first over a catalyst comprising acrystalline mordenite of reduced alkali metal content and ahydrogenating component selected from metals of Group VI and V111 of thePeriodic Table to remove n-paraffin wax and then passing the totalreaction product also at 260482 C and 50 3,000 psig over a catalystcomprising a refractory inorganic oxide and a hydrogenating componentselected from metals and compounds thereof of Group VI and VIII of thePeriodic Table to remove sulphur.

The two catalysts may be in the same reactor e.g. in a downflow reactorthe top portion may contain a bed of the nparaffin wax removal catalystand the lower portion a bed of the desulphurisation catalyst.

It is important to carry out the process in the sequence stated. Themordenite n-paraffin wax removal catalyst is not sensitive to sulphurcompounds present in the feedstock and does not convert these compoundsto hydrogen sulphide. It is sensitive however, to hydrogen sulphideproduced by the desulphurisation. The feedstock must, therefore, contactthe mordenite first and, as stated above, the hydrogen used must besubstantially free of sulphur. In the preferred single reactor system,this may be achieved either by using once-through hydrogen or, whenrecycle of hydrogen is practised, by scrubbing the recycle gases toremove hydrogen sulphide produced by the desulphurisation. Alternativelya two-reactor system may be used with hydrogen being fed once-through inthe first n-paraffin removal reactor and-hydrogen being recycled in thesecond sulphur removal reactor. The hydrogen sulphide content of theinlet hydrogen is preferably less than 1,000 ppm by volume and moreparticularly less than 200 ppm by volume. Suitable methods for removinghydrogen sulphide from recycle gas streams include washing with alkalinematerials such as caustic soda, or an amine such as diisopropylamine orabsorbtion on a solid material such as zinc oxide or a molecular sieve.

The ratio of n-paraffin wax removal and sulphur removal catalysts in thesystem will depend on the relative amounts of the two components in thefeedstock and the degree of removal required. It may vary from -90% volof n-paraffin wax removal catalyst and 90-10 percent vol. of sulphurremoval catalyst, preferably 20-60 percent of the former and 80-40percent of the latter.

The preferred temperatures and pressures for both catalysts are 343-427C and 250- 1 ,500 psig. Other process conditions, again for bothcatalysts, may be chosen from:

Overall space velocity 1-20 v/v/hr, preferably 2-8 v/v/hr Hydrogentreating rate 25010,000 SCF/B, preferably 2000- 8000 SCF/B. Theindividual space velocities with each catalyst will depend on therelative amounts of each used. With the preferred amounts of 20-60percent vol. of n-paraffin wax removal catalyst and 80-40 percent vol.of sulphur removal catalyst the individual space velocities may be:N-paraffin wax removal catalyst 1-40 v/v/hr preferably 2-16 v/v/hrSulphur removal catalyst l40 v/v/hr preferably 2-16 v/v/hr Thefeedstocks may be petroleum fractions boiling in the range 30650 C i.e.,the gasoline, kerosine, gas oil and wax distillate fractions of crudeoil. Such fractions are likely to have sulphur contents in the range 0.13.0 percent wt. and nparaffin wax contents in the range 5 to 50 percentwtfand these can be reduced by the process of the present invention tolevels of 0.01 0.3 percent wt. sulphur depending on the sulphur contentof the feed and n-paraffin wax contents of 0 to 10 percent wt. againdepending on the n-paraffin wax content of the feedstock and theseverity of the catalytic treatment. The process is particularlysuitable for the production of gas oils of 250 to 400 C ASTM boilingrange suitable as diesel fuels or fuel oils.

The n-parafiin wax removal process and catalyst may be broadly asdescribed in UK. Patent specification Nos. 1,088,933 and 1,134,014. Theterm "crystalline mordenite of reduced alkali metal content means,preferably, a mordenite with an alkali metal content of less than 3percent wt., more particularly less than 1.5 percent wt. The deficiencyof alkali metal cations can be made up with other metal cations forexample Group II metal cations, particularly magnesium, or rare earthmetal cations. Preferably however the mordenite is a decationizedmordenite," which means a mordenite having a deficiency of metalcations. An alternative term in the art is hydrogen mordenite, since itis assumed that when metal cations are removed they are replaced byhydrogen ions.

Natural or freshly prepared synthetic mordenite has the formula:

where Me is a metal cation, n is the valency of the cation and X isvariable between nil and 7 depending on the thermal history of thesample. In natural mordenite or freshly prepared synthetic mordenite Meis commonly an alkali metal, particularly sodium.

Decationization can be achieved by exchange of the alkali metal cationswith ammonium ions followed by heating at e.g., 250600 C to drive offthe ammonia. With this method of decationization alkali metal contentscan be reduced to less than 0.5 percent wt. An alternative method istreatment with an acid to decationize the zeolite directly. Suitableacids are hydrochloric or sulphuric acid. Acid treatment may not removethe alkali metal cations to the same extent as ammonium exchange butthis is not necessarily disadvantageous and it is not difficult toreduce the alkali metal content to below 1 percent wt. If the acidtreatment uses strong acid of from 5-50 percent wt. strength preferably10-20 percent wt strength, an additional effect is obtained, in thataluminum is removed from the crystal lattice with a consequent increasein the silicaaalumina ratio. For example, the normal silicazaluminaratio of9-l 1:1 can be increased to 14:1 or more. FIGS. ofas high as :1have been reported, but the preferred range is 14:1 to 50:1. Increase oftime, temperature and acid strength increases the aluminum removal and aconvenient acid treatment is with 10-20 percent wt. acid under refluxfor 212 hours.

After either form of decationization the mordenite is desirably washedto remove excess acid or ammonium exchange solution and is heated to250-600 C.

It should be emphasized that mordenite with higher than normalsilicazalurnina ratios retain the crystal structure of mordenite and arenot significantly altered in terms of physical strength, stability orcrystallinity.

The hydrogenating component is preferably a platinum group metal,particularly platinum or palladium, and it is preferably added byion-exchange. The amount of the platinum group metal is preferablywithin the range 0.01 to 10 percent wt., particularly 0.1 to 5 percentwt.

The catalyst is preferably calcined at for example 250600 C in dryflowing air before use to remove any water and to eliminate any ligandsattached to the hydrogenation component. It may also be reduced in astream of hydrogen at 250600 C.

The n-paraffin wax removed are cracked to lower-boiling nparaffins,largely C, and C paraffins with possibly some C -C hydrocarbons. Thesematerials may be readily separated from the product by distillation,particularly if the feedstocks are kerosine or higher boiling fractions,and are themselves valuable as LPG and petrochemical feedstocks.

' In the sulphur removal catalyst, the refractory inorganic oxidesupport is preferably an oxide of an element of Groups I], ill and IV ofthe Periodic Table or a mixture of such oxides. The preferred support isalumina. The hydrogenating component is preferably an oxide or sulphideof a Group Vlb metal (i.e., tungsten, molybdenum and chromium) togetherwith one or more oxides or sulphides of the iron group metals (i.e.,cobalt, nickel and iron). The amounts may be from 2-25 percent wt. ofthe Group Vlb metal, expressed as metal, and 01-10 percent of the irongroup metal or metals, also expressed as metal. Preferred catalystscontain molybdenum oxide or sulphide together with cobalt and/or nickeloxide or sulphide.

EXAMPLE 2 A gas oil having an ASTM boiling range of 242 to 450 C waspassed downwards over a dual catalyst bed using the catalysts of Example1 but in a ratio of 50 percent vol. Pt-H- mordenite (top half) and 50percent vol. Co-Mo-alumina (bottom half).

The-conditions used and the results obtained are set out in Theinvention is illustrated by the following examples. Table 2 below' TABLE2 Hours on stream EXAMPLE 1 Feed 0-250 260-420 Bed temperatures:

Mordenitc bed, top, C 372 373 A heavy gas oil was passed downwards intoa reactor con- $83233: Egg {fig gf taining a dual catalyst bed. The toponethird of the bed was a 80- 04 0 alumina lgeg, to 1%. 284 ooaumina e,m .J 0 platinum-hydrogen mordenite catalyst and the bottom two- COMOalumina bed 'o C 410 405 thirds a cobalt and molybdenum oxides analumina catalyst. Pressureip.is .i.g( .munnnyH 1,208 1,208

' Saceveocyover ,vo.vo. Inspec tron data on the two catalysts which hadbeen calcined p Over mordenite VOL/VOL h g at 550 C were as follows.Over Co-Mo alumina, vol./vol. h. 6.0 6.0 Once through gas rate,s.c.f./brl 5,000 3, 000 Unstabilized product (HzS free):

Yield on feed, percent wt 100 00.0 92. 4 Pour point, C +7 (5)Pt-H-mordenite catalyst C yLfl -AI O catalyst Sulphur t percent wt e 91(a) l (d) 5 -23 to l8. -15 to 10. "0.3 to 0.4. 0.4 to 0.5.

Pt wt. 0.46 Co wt. L9 40 Na% wt. L Mo wt. 10.4 Si wt. 39.8 A1 0 wt. 86.0Al wt. 4.58 Surface Area mlg 244 Again the products show appreciablereductions in sulphur g fr a n 2: 6 Pore Yolume /g- 0.31 content andn-paraffin wax content (as demonstrated by the gi sg z'zi 0 lower pourpoint). As compared with Example 1, the in- 45 creased amount ofPt-H-mordenite catalyst relative to the Co- Mo-alumina catalyst hasgiven a greater reduction in pour point. The beneficial effect of ahigher gas rate (5,000 as against 3,000 SCF/B) is also shown.

Details of the feedstock, the process conditions used and The followingcomparative example shows the importance theresults obtained are given.in Table 1 below. of keeping the mordenite catalyst out of contact withH 8.

TABLE 1 Hours on stream 8-96 109-213 224-272 296-352 364-444 454-558569-585 Feedstock:

Boiling range, C. AS'lM 278-345 242-460 Pour point, F. 45 45 45 45 45 4545 Sulphur content, p re 1. 83 l. 83 l. 83 l. 88 l. 88 l. 88 l. 88Process conditions: Pressure, p.s.i.g 500 500 500 500 500 500 500Hydrogen rate (once through), S 5, 000 5, 000 5,000 5, 000 5, 000 5, 0005, 000 S-eontent oi hydrogen, p.p.m Nil Nil Nil Nil Nil Nil Nil Overallspace velocity, v./v./hr 4. 0 4. 0 4. 0 4. 0 4.0 2.0 2. Space velocityon It-H mordenite 12.0 12.0 12.0 12.0 12.0 6. 0 8. 0 Space velocity onCO-MO-AIQOB 6.0 6. 0 6.0 6. 0 6.0 3.0 4.0 Temperature, F 700 750 725 725750 750 750 Unstabilised product boiling above 177 C..-

Yield, percent wt 88. 6 87. 5 84. 4 87. l 88. 4 80. 4 81.6 lour point, F20 20 35 35 35 15 30 Sulphur content, percent wt 0. 59 0. 28 0. 25 0.33O. 24 0. l8 0. 20

The wax content is defined as the amount of material EXAMPLE 3precipitated from methylene chloride solution at -25 F. in this method aknown Weight of i i dissolved in h The gas oil of Example 2 was usedwith the catalyst bed of methylene chloride in a flask, the ratio ofmethylene chloride to oil being 10:1. The solution of oil in methylenechloride is then cooled to 25 F and held at this temperature for 30minutes. The precipitated wax is separated by filtration, washed withmethylene chloride at 31 25 F until the filtrate is Example 1. Theprocess was started off with once through hydrogen, then switched tounscrubbed recycle hydrogen and eventually back to once through hydrogenagain. The conditions used and the. results obtained are shown in Table3 below.

TABLE 3 Hours on stream Feed 160-310 315-330 330-370 370-390 390-470 480670 Temperature, C 390 390 390 399 399 399 Pressure, p.s.i.g. 500 500500 500-1, 000 1,000 l, 000 Space velocity over, voL/vol. h. 12.0 12.012.0

Gas rotc'once through, s.c.f./brl 5, 000 5, 000

Gas rate-(unscrubbed) recycle, s.c.f./brl H S content of recycle gas,percent vol... Hz content of recycle gas, percent vol Unstabllisedproduct (H S free):

Yield on feed, percent wt Pour point, C .t. Sulphur content, percent wt1 to --7. 4 Pressure changed to 1,000 p.s.l.g. over ll. 2 0.4 to 0. 1. I5 Switch to encep percent through.

3 Switch to recycle over 16 h.

After a settling in period, the product over the period 150 to parafi'lnwax to lower boiling n-parafi'lns, then passing the total 310 hours onstream showed an improved pour point and reaction Product at atemperature of 2600-482" i at a P reduced sulphur content. When the exithydrogen with a H S 20 sure of 50 3,000 P gi and at a Space l y of /hl'content of 3.5 percent, was recycled, however, the pour point through aSecond Catalyst bed comprising alumina and a reducing activity wasquickly killed, although desulphurisation hydrogonating componentselected from a Group K metal continued. Increasing the pressure to1,000 psig effected no and compounds thereof and an iron group metal andimprovement d h recycle was stopped d once. pounds thereof of thePeriodic Table to remove sulphur, the through hydrogen used again therewas also no significant imamount of Said Wax removal catalyst being 20to 60 Percent provement, showing that the deactivation of the mordeniteVolume of the total catalyst and the amount of the Sulphur catalyst waspermanent and not temporary. removal catalyst being 80 to 40 percentvolume of the total The same effect would occur if the order of thecatalysts Catalyst and separating diesel fuels fuel Oils from the werereversed and the H 8 containing products from the Sulphur-removedProduct desulphurisation allowed to contact the mordenite. A Process asclaimed in elaim 1 wherein the two catalysts w l i are disposed in thesame reactor.

1. A hydrocatalytic process for the removal of sulphur ar d Pf asclaimed in claim 1 wherein the Overall Space n-parafi'ln wax from gasoil fractions to render such a fractions veleelty 2 8 V/V/hl' and thehydrogen eating rate is 2,000

suitable for use as diesel fuels or fuel oils comprising passing a 3,000petroleum gas oil fraction boiling within the range 250 to A PmeeSS asclalmed clam! 1 wherem the 'p 450 C and having a sulphur content of 0.1to 3.0 percent wt eatalysteohfprises to 10 P e wt of a and a n-parafi'lnwax content of 5 to 50 percent wt. together Platlhum 8 metal h saldeteeatlehlzed mmdehltewith hydrogen which is substantially free ofhydrogen sulphide A PmeeSS as elalmed elem 1 wherein the Sulphur at atemperature of Z60 48Z C at a pressure f 50 3 000 40 removal catalyst isan oxide or sulphide of a Group Vlb metal, psig, and at a space velocityof 2-16 v/v/hr through a first Present in 2 25 Percent Wt expressed asmetal, and one of catalyst bed comprising a crystalline mordenite ofreduced almore oxides of sulphides of the iron g p metals, Present inkali metal content of less than 3 percent and containing a to 10 Percentwt expressed as metal supported hydrogenating component therein selectedfrom metals of Groups VI and VIII of thePeriodic Table to convert said11- at TS'ICATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. 3-,668 ,113 I I Dated June 6 1972 In ento Bernard Whiting Burbi dge et a1It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col. 2, Line 53, for "FIGS." read Figures Col. 3, Lines 1 and 2, for"n-paraffins read n-paraffin wax Cols. 3 and 4, TABLE 1. Under col.headed 109-213, for "750" read 725 under col. headed 224- 272 for "725"read 750 under col. headed 224- 272, for "35" read 20 C01. 3, Line 75,for "31 25F" read -25F Col. 5', Line 20, for "H S" read H 8 Col. 5, Line33, 2 for "such 8. fractions" read such fractions Signed and sealed this9th day of January 1973.

(SEAL) Attest;

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attestlng Officer Commissionerof Patent:

FORM PO-IO O I USCOMM-DC seam-ps9 U.S, GOVERNMENY PRlNTlNG OFFICE: 1969O-366-334

2. A process as claimed in claim 1 wherein the two catalysts aredisposed in the same reactor.
 3. A process as claimed in claim 1 whereinthe overall space velocity is 2 - 8 v/v/hr and the hydrogen treatingrate is 2,000 - 8,000 SCF/B.
 4. A process as claimed in claim 1 whereinthe n-paraffin wax removal catalyst comprises 0.01 to 10 percent wt of aplatinum group metal in said decationized mordenite.
 5. A process asclaimed in claim 1 wherein the sulphur removal catalyst is an oxide orsulphide of a Group VIb metal, present in 2 - 25 percent wt expressed asmetal, and one or more oxides or sulphides of the iron group metals,present in 0.1 to 10 percent wt expressed as metal, supported onalumina.